Hybrid drives for work machines comprise a combustion engine, a generator driven by a combustion engine, a charge storage device and an electric motor. The propulsion of the work machine or the driving of components driven by the work machine is ensured by a power train in which the driving torques of the combustion engine and of the electric motor are superposed by a summation gear, as a rule a planet gear, or they act jointly on a shaft. By distributing the driving power to the power provided by the combustion engine and the power provided by the charge storage device. Such hybrid drives provide an additional freedom in comparison to conventional drives, in which only the power of the combustion engine can be changed. In order to specify the torque of the combustion engine and the torque of the electric motor, or to distribute a power to be provided to the combustion engine and to the electric motor, different types of regulators are known to be used, and in particular proportional-integral regulators or heuristic regulators.
These so-called power or torque distribution regulators have to take into consideration other general conditions such as maintaining a certain charge in the charge storage device, and have to be optimized in the sense of an optimization of the overall level of efficiency. Since a preview of the future power need of the work machine is not possible, as would be required for an optimal regulator taking into consideration all the circumstances, control parameters of the regulators (referred to as suboptimal regulators) are specified in such a manner that they work with the most optimal level of efficiency possible for the power demand in the case of a predetermined cycle. Accordingly, in the case of a proportional-integral regulator, for example, the factors, with which the power demand is included proportionally and integrally in the output value for the distribution of a power to be provided to the combustion engine and to the electric motor, are optimized for the predetermined cycle.
Work machines usually run through different work cycles in the context of the activities to be performed. For example, when spreading manure the load is relatively low, in the case of bale pressing the load is cyclical, alternating between a relatively low and relatively high load, and for plowing the load is relatively high. The adaptation of the control parameter of the regulator is not optimal for all work conditions or states.
In one known example, a method is provided for the adaptive control of a hybrid vehicle whose combustion engine drives a generator which in turn supplies a charge storage device and an electric motor, the latter alone being used to propel the vehicle. A controller compares a work procedure with a stored reference work procedure in order to determine in which load category the hybrid vehicle is being operated and selects a current control curve and a current rise curve for the operation of the electric motor as a function of the respective load category. The user can additionally specify which task is to be accomplished at a given time, and the controller selects the respective load category as a function of the task. Accordingly, on the one hand, a manual input for the respective cycle may be used and, on the other hand, only the current uptake of the electric motor is controlled; thus no adaptation of the control parameters of a regulator occurs.
Thus, a need exists for refining a method for determining a control parameter of a power or torque distribution regulator for a hybrid drive of a work machine and of a corresponding power or torque distribution regulator.